Histidine-containing protein (HPr) is a central metabolic sensor in low-GC Gram-positive bacteria and plays a dual role in sugar uptake by the phos-phoenolpyruvate–sugar phosphotransferase system and in transcriptional control during carbon catabolite repression. The latter process is mediated by interaction between HPr and the carbon catabolite repression master transcription regulator, carbon catabolite protein A (CcpA), a member of the LacI-GalR family of DNA-binding proteins.
